omdStepVisualizerHighlighting

Manages the highlighting of nodes within mathematical expressions displayed by the omdStepVisualizer. It uses a robust tree differencing algorithm to identify changes between consecutive steps and highlights affected nodes, providing visual feedback on transformations.

Class Definition

export class omdStepVisualizerHighlighting

Constructor

new omdStepVisualizerHighlighting(stepVisualizer)

Creates a new omdStepVisualizerHighlighting instance.

• stepVisualizer (omdStepVisualizer): The step visualizer instance this highlighting manager is associated with.

During construction, it initializes a Set to track highlightedNodes and sets educationalMode to true by default.

Public Properties

• stepVisualizer (omdStepVisualizer): The associated step visualizer instance.
• highlightedNodes (Set<omdNode>): A set of omdNode instances that are currently highlighted by this manager.
• educationalMode (boolean): If true, enables highlighting of pedagogical simplifications (e.g., intermediate steps that might be skipped in a final solution). Default: true.

Public Methods

highlightAffectedNodes(dotIndex, isOperation = false)

This is the main method to trigger highlighting. It compares the equation at dotIndex with the previous visible equation in the sequence to identify changes and then applies appropriate highlighting.

• dotIndex (number): The index of the dot (step) for which to highlight affected nodes.
• isOperation (boolean, optional): If true, indicates that the step is an operation (e.g., adding to both sides), which affects how provenance is highlighted. Default: false.

How it Works:

1. Clear Existing Highlights: First, any previously active highlights are cleared.
2. Identify Equations: It determines the currentEquation (associated with dotIndex) and finds the previousEquation (the nearest visible equation before the current one).
3. Tree Differencing: It uses omdTreeDiff.findChangedNodes to perform a robust comparison between the previousEquation and currentEquation. This algorithm identifies nodes that have been added, removed, or modified.
4. Direct Highlighting: Nodes identified as directly changed by the diff algorithm are highlighted with a primary explanation color (omdColor.explainColor).
5. Provenance Highlighting: For non-operation steps, the system traces the provenance (history) of the directly changed nodes back to their origins in the previousEquation. These originating nodes are then highlighted with a secondary provenance color (omdColor.provenanceColor), visually connecting the transformation.

clearHighlights()

Removes all active highlights managed by this class from the expression tree. It iterates through all highlightedNodes and calls setExplainHighlight(false) on them, then clears its internal highlightedNodes set.

Internal Methods

• _highlightNode(node): Applies the standard explanation highlight color (omdColor.explainColor) to a single omdNode by calling its setExplainHighlight(true) method and adds the node to highlightedNodes.
• _findNearestVisibleEquationAbove(currentIndex): Searches backward from currentIndex in the stepVisualizer.steps array to find the closest omdEquationNode that is currently visible.
• _highlightProvenanceNodes(changedNodes, previousEquation): Iterates through changedNodes and their provenance chains to identify and highlight corresponding nodes in the previousEquation with omdColor.provenanceColor. It uses rootNode.nodeMap for efficient node lookup and a visited set to prevent redundant processing.
• _belongsToEquation(node, targetEquation): Checks if a given omdNode is part of the subtree of a targetEquation by traversing up its parent chain.
• _highlightProvenanceNode(node): Applies the secondary provenance highlighting style (omdColor.provenanceColor) to a single omdNode by calling its setExplainHighlight(true, omdColor.provenanceColor) method.

Example

This class is typically used internally by omdStepVisualizer when a step dot is clicked:

// Inside omdStepVisualizer's _handleDotClick method:
this.highlighting.highlightAffectedNodes(dotIndex, isOperation);

// Inside omdStepVisualizer's _clearActiveDot method:
this.highlighting.clearHighlights();